Indefinitely long potentiometer



April 3, 1962 P. LUGER 3,028,572

INDEFINITELY LQNG POTENTIOMETER Filed Feb. 23, 1951 5 Sheets-Sheet 1 o N n 1- m \o m N n En r1 I-'l r1 J- FS a* 56 )74? 4647 5? bbd/ h 5 l #5f l 55 QE y ZI Z2g '/7 3 ATTORNEYS 3 Sheets-Sheet 2 Filed Feb. 23, 1961 NGN INVENTOR PAUL LUGER ATTORNEY April 3, 1962 P. LUGER 3,028,572

INDEFINITELY LONG POTENTIOMETER l Filed Feb. 23, 1961 3 Sheets-Sheet 5 PAUL LUGER BYGMm/L/ ATTORNEY5 United States Patent O ice 3,02s,s72 INDEFINTIELY LUNG PGTENTIOMETER Paul Luger, 801 th Ave., Seattle, Wash.

Filed Feb. 23, 1961, Ser. No. 91,112 18 Claims. (Cl. 338-176) The present invention relates to impedance instruments such as resistance boxes,"potentiometers or the like and more particularly to an improved switching arrangement of the impedances of, and in such instruments.

The apparatus which is a principal object of the present invention utilizes as a basic stage, a combination of a resistance device and a switch member. A plurality of such stages'rare normally connected together between certain terminals of the switching device to form an arrangement which may be used as a potentiometer or as a simple resistance box. In addition, a suitable rneostate or basic potentiometer connected to the circuit may be provided. Such an arrangement, with or without a basic rheostat is called an indefinitely long potentiometer or simply a long potentiometer. The long potentiometer l may be used either as a potentiometer or a resistance box.

The resistance box provided in accordance with the present invention permits the attainment of resistance values over a range from that of the smallest value of any resistance present up to the total of all of the resistances together, whereby the number of resistances added or to be added is not, limited. Decimal or binary systems of resistance values are preferred but not necessarily employed.

A potentiometer incorporating the features of this invention permits the attainment of a large range of values with relatively few resistance elements to be employed which values would normally require a great plurality of resistances. In essence, a potentiometer incorporating the principles of the invention provides an equivalent potentiometer of great length, and, in fact, the potentiometer length may be termed indefinite since the resistance maybe doubled readily by the provision of an additional stage which additional stage is basically as similar as any of the stages already present in the system wl ile only the particular resistor of this additional stage :has twice the magnitude of the highest resistor already present therein. Doubling the value of previous resistances in a chain of resistance elements together with the addition of a switch member is eective to provide in the usual case a continuous range of resistances forthe long potentiometer.

An apparatus in accordance with the present invention includes resistance boxes, potentiometer combinations, motor driven or hand operated rotating potentiometers, as well as resistance boxes and potentiometers to which specific reference has been made.

Utility is found of these instruments in `the field of applications which are common to resistance boxes and potentiometers, and definite advantages are attributable to the apparatus of this invention.

For example, a potentiometer incorporating the feature of this invention exhibits a particular advantage in that any load at the output end thereof has substantially no effect on the reliability-or ease of reading even when the potentiometer -is loaded at its output. In this feature .the long potentiometer is a great improvement on a Kelvin-Varley circuit which, in general, should not be loaded. This and other features of the device, in accordancerwith the present invention, renders it useful in meter applications, Wheatstone bridges, circuits requiring variable grounds such as quadrant quartz fiber, electrometer, or a power supply, and in fact in areas where potentiometers are required to possess ygood reproducibility, substantially 3,628,572 Patented Apr. 3, 1962 indefinitely large resolvability and even in circuits where the potentiometer is loaded.

The resistance-box application, the switch member associated with the resistance device of a particular stage incorporates means for including or excluding the resistance vdevice of that stage from the circuit while yet providing for the application of power to a succeeding stage through the same switch member. In addition, in potentiometer application, the switch member provides for the positioning of the conventional potentiometer of the resistance device in the desired position relative to other resistance devices of the circuit of the apparatus. Furthermore, a simplified setting arrangement is achieved in an apparatus according to the present invention by the relationship ofthe resistance devices and the switch members. f

According to the foregoing it is an object of the present invention to provide a new and improved resistance-boxpotentiometer which can be readily made into a resistance box or potentiometer of indefinite length.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the object of the invention and further objects and the advantages thereof will be better understood from the following description taken in connection with the accompanying drawing in which:

FIGURE l is a schematic circuit diagram of a iirst embodiment in accordance with the present invention particularly designed for a potentiometer of the rotary typein which movable contact sections or segments are shown in development;

FIGURE 2 illustrates various schematic diagrams of the potentiometer illustrated in FIG. l and different settings thereof;

FIGURE 3 is a front View of a switching member arrangement which might be used as a particular embodiment of (a portion of) the resistance box-potentiometer illustrated in FIG. l;

FIGURE 4 illustrates another embodiment of the present invention;

FIG. 4a illustrates a supplemental circuit network for thepembodiment shown in FIG. 4; and

FIG. 5 illustrates an embodiment of the present invention modified as compared with FIG. 4.

`Turning now to FIGS. l and 2 there is illustrated a plurality of contact segments 11, 12, 21, 22, 31, 32, 41, 42, 51 and 52 which segments may be mounted around the circumference of a cylindrical, insulating drum 70. However, the segments may also be Contact slips mounted in pairs of insulating discs in a rotary switch and positioned on a common shaft in axially aligned relationship.

Turning briefly to FIG. 3, there is shown contact segment 11', which corresponds to contact 11 of FIG. l, mounted on an insulating rotary member 74 which is positioned on a shaft 73 which is the just mentioned common shaft. The shaft 73 is appropriately supported and provided with a handle (not shown) for rotating the inner disc 74 which is attached to and carries the contact ksegment 11. This disc 74 rotates about the stationary member 70.

The long contact clip 11 actually defines 3 concentrically positioned paths around the axis of said 73. The center path thereto is scanned by a sliding contact 14 corresponding to a brush which in FIG. l has reference numeral 14 and is to slide on a segment 11. The outer path of strip 11 is slided upon by a contact 15' corresponding to a brush designated by reference numeral V15 in FIG. l and the inner path is slided upon by a contact 13 corresponding to a brush designated in FIG. 1 with reference numeral 13. A similar segment 12,' (not 3 shown) would be mounted on the other side of disc 70', of FIG. 3, corresponding to 12 of FIG. 1.

Turning now back to FIG. l, the segments are arranged in pairs as illustrated; they are shown in development. Two segments pertaining to each pair are of `similar configuration. There are slider contacts or brushes 13, 14, 15, 16 and 17 associated with the two contact segments 11 and 12. The contact brushes 13, 14 and 15 are to slide over segment 11, `while the contact brushes and 16 and 17 are to slide over segment 12.

In a similar manner, contact brushes 23, 24, 25, 26 and 27 are associated with the segment pairs 21 and 22; contact brushes 33, 34, 35, 36 and 37 are associated with segment pairs 31 and 32; Contact brushes 43, 44, 45, 46 and 47 are associated with segment pairs 41 and 42; and contact brushes 53, 54, 55, 56 and 57 are associated with contact segments 51 and'52. Y

Turning back for a moment to FIG. 3 and the actual segments, it will be apparent, that if segments 11' and 12' (latter not shown) vcorresponding to 11 and 12 of FIG. 1 are mounted on opposite sides of supporting disc 70' and if 12' is turned face down in relation to its appearance at 12 in FIG. 1, then, contact 15' in FIG. 3 will make contact with 12 and not with 11' for the switch position shown by FIG. 3. Moreover, corresponding with 13' and 14 on the upper side of FIG. 3 there will be two contacts on the reverse side of FIG. 3, 16 and 17', which are not shown, but would correspond to contacts 16 and 17 in FIG. 1.

It will be noted that brushes 14 and. 16 (latter not shown) ride the center path of 11' and are insulated from one another as are brushes 14 and 16 in FIG. 1. It ,may also be noted that brushes 13 and 17" (latter not shown) are mounted opposite each other and are interconnected and may be brought out through one solder lug 62.

In reality 13' and 62', 14' and 18', and 15 and 61 are three metal connectors mounted on '70 and adjusted to make contact each with the rotating segment 11' at various settings of the ten possible positions of the switch. Evidently there are various ways in which contacts 11' and 12' could be mounted. For example, each could be mounted on one wafer by itself or both could be mounted on the same side of a wafer switch with appropriate contact brushes. Again 11 could be designed so that there would be no inner path but a strip of 20 contact positions could be provided so that the inner path would occupy` positions from 11 to 20. f

Referring now to FIG. l, the numerals 0i, 1, 2, 3, 4, 5, 6, 7, 8, and 9, written on the left and right hand side of FIG. 1 designate particular positions of the Contact segnected to the two contact brushes 23 and 27; it will be appreciated that there be interconnected contact terminals between this connection. Contact brush 26 is directly connected to contact brushes 3.3 'land 37 and eventually, interconnected contact terminals are interposed therebetween. Contact -br'ush 36 is directly connected to contact brushes 43 and 47, and contact brush 46 is directly connected to contact brushes 53 and 57 via line 66.

There are five resistances designated with reference numerals 10, 20, 30, and 10', respectively. These numerals may also designate the ohmic value of these particular resistances,'whereby, of course, the two resistances 10 and 11) both have the ohmic value ten.

Resistance Stl interconnects contact brush 14 and contact brush 25. Resistance 30 interconnects contact brush 24 and contact brush 35. Resistance 2u interconnects contact brush 34 `and contact brush 45. Resistance 10 and line 65 interconnects contact brush 44 and contact brush 55, and resistance 10' interconnects the brushes 54 and 56. Resistance 10 actually is a potentiometer having a glider which is connected to terminal 64.

if the device as shown is not to employ a rheostat or basic potentiometer, the two lines 66 and 65 will be interconnected directly, thus excluding potentiometer 111'; this interconnection is indicated by the dashed line. In this case, the alternative terminal 63 is to be connected to the innerconnection of the two lines 66 and 65.

Looking at the assembly as illustrated, it is apparent that each pair of segments is associated with aresistor and ve contact brushes; two of the brushes are inter-` connected directly, one brush is connected to the associated resistor, another brush lis connected to the resistor l of the preceding stage and the fifth brush is connected to the interconnected pair or" brushes of thesucceeding stage.

It will be apparent that in this manner there is no limitation as to the number of assemblies (each consisting of two elongated Contact segments, tive contacts and a re sistance) which could be interconnected in a circuit arrangement. Of course, the first one of these assemblies ditcrs in that the interconnected brushes 13 and 17 are connected to one main terminal (62 in PIG. l) while another brush 15, usually connected to a preceding stage resistor, is here connected to the second main terminal, 6.1.

In FIG. 1 the parts are shown in development. It is understood now that the switch movement will require that the contacts shown on the horizontal line trom 13 to 57 in FIG. 1 are to make contact through the switch segments 11 through 52. These contacts may assume one of ten positions from zero to nine as shown in FIG. l.

The current paths of several settings of the potentiometerillustrated in FIG. l are schematically shown in FIG. 2.. In FIG. 2, the circuit on top illustrates the current paths for setting zero as indicated to the left of this drawing. The current passes through the following circuit elements at this setting zero; brush 15, contact segment 12, brush 16, direct connection to brush 27, contact segment 22, brush 26, direct connection to brush 37,contact segment 32, brush 36, direct connection to brush 47, Contact segment 42, brush 46, direct connection to brush 53, contact segment 51,-brush 54, connection to potentiometer 10'; alternatively the brush 46 might be connected directly to the main terminal 63; if the potentiometer 10 is used, output terminal 64 is served therewith. Continuing, in case of using potentiometer 10', the next connection is to brush 56, then over to contact segment 52, brush 55, resistor 11D, brush 14, contact segment 41, brush 45, esistor 2u, brush 34 contact segment 31, brush 35, resistor 3d, brush 24, contact segment 21, brush 25, re-

sister 5d, brush 14., contact segment 11, brush 13, and t0 the main terminal 62.

It will be observed that between the terminals 61 and 64 or 63 the resistance value zero may be derived. If the potentiometer 19' is used not only the resistance val-ue zero but resistance values between zero and then ohms at intervals as determined by the division of this potentiometer maybe taken between terminals 61 and 64.

The circuit below the above described circuit illustrates the settings one which means one step of rotating the potentiometer (i.e. moving the segments one step upward in the direction of the arrows in FIG. 1). In this case the circuit paths from terminal 61 run over the Vfollowing elements 15, 12, 16, 27, 22, 26, 37, 32, 36, 43, 41, 44, then comes the resistor 10 which is connected to brush 55, the circuit continues over elements S1, 54 and potentiometer 10 of output 64,` alternativelythe circuit continues including elements 56, 52, 57, 46, 42, 4S, re-

sistor 2d, elements 34, 31, 35, resistor 311, elements 24, 21,

25, resistor 50, brush 14, segment 11, brush 13 and output terminal 62.

It will be apparent from the setting that between the terminals 61 and 64, the xed resistor of ten ohms appears, while the resistor permits settings between zero and ten; values between 10 and 20 according to the division of this potentiometer 10', can now be taken from the terminals 61 and 64.

The next setting, the setting two is illustrated in the circuit diagram below. path runs first over the following elements 15, 12, 16, 21'7,

22, 26, 33, 31, 34; then appears the resistor 20 which en its other side is connected to elements 4S; the current path proceeds over elements 42, 46, 53, 51, 54, potentiometer 10' and alternatively either to output terminal 64 or over the remainder of potentiometer 10 and the following elements: 56, 52, 55, resistor 10, elements 44, 41, 43, 36, 32, 35, 30, 24, 21, 25, 50, 14, 11, 13 and output terminal 62.

It will be observed from this circuit connection that now at this setting tv/o, thev Xed resistor (ohm Value twenty) appears between the terminal 61 and 64, while in addition yagain the potentiometer or more precisely a particular portion thereof as desired is connected in series tothe resistor 20 and appears also between output terminals 61 and 64.

It will further be observed that the setting two is distinguished from the setting one in that the resistor 10 is again reconnected so as to appear between the terminals 64 and 62. Looking at the settings Zero, one and two together, it will be observed that with this continuously changed setting, there is no successive adding of resistances between the main terminals 61 and 64, but suitable resistances are inserted in circuit between these terminals'such as resistor 10 in setting one and resistor 20 in setting two, while, on the other hand, the rcsistances not needed for a particular setting remain or are reconnected into the series circuit connection between main terminals 64 and 62.

From FIG. l it will be apparent, that in the next setting, which is setting three, vresistor is connected between the terminals 61 and 64; then for the setting four the vresistor 10 is added; for setting ve, resistors 30 and 10 are taken out again and resistor is added; ffor the setting six resistor V10` is added; for setting seven resistor 16s is tal/:en out `again and resistor 20 is added; for setting eig-ht resistor 20 is taken out again and resistor 30 is added; for setting nine resistor 50 and 30 remain between the terminals 61 and 64 and resistor 10 is added. This latter setting is explicity shown in FlG. 2, bottom illustration which shows the current path yfor this setting nine and will be fully understood from all the explanations given above.

It will be observed that for these decade rotary switch positions, every time that resistor 30 is in circuit between terminals 61 and 64 While both resistors 10 and 20 are not in circuit, such positioning can be reversed, leaving resistor 30 out and instead placing resistor 10 and 20 between terminals 61 and 64.

.lt will further be observed that one could provide for a setting ten in which, as compared with ythe setting nine, the resistor 20 is in circuit between the terminals 61 and 64 while resistor 10 is in its initial connection between terminals 64 and 62.

It will further be observed that this decade rotary switch serving for a continuous setting between zero and nine can be connected to a similar `circuit which is distinguished from the one shown in FIG. l in that the resistances have the ohmic values 500, 300, 200 and 100, without any additional potentiometer, but with a utiliza- `tion of circuit line connections corresponding to the lines 65 and 66 in FIG. 1. These corresponding lines of such 500-300-200-100 resistance box ywould then be connected to the terminals 61 and 62 of the FIG. l, and the corresponding main terminals of this resistance box V(5(50-300-200-100) Would take over the Part which From terminal 61, the currenty 6 the terminals 61 and 62 have in FIG. 1. With such a combination, one would obtain a potentiometer with which one can set every value between zero and 1,000 ohms with steps as defined by the steps of the potentiometer 10 in FIG. l.

It will `further be observed `that the decimal system is obtained in the present case in properly combining the digits l, 2, 3 and 5 (or in this case 10, 20, 30 and 50). It is readily apparent `from t-he drawing and 1the entire disclosure of the specification, that a selection 1--1--2-5 or selection l-l-3-5 is also possible.

It may be noted here, referring to Fig. l, that the switch assembly attached to the basic rheostat 10' has the purpose of always directing the current through the rheostat 10 in the same direction. This is important if the dial of the rheostat is to read correctly `and is not calibrated in both directions.

The device shown in FIG. 1 is readily capable of advantageous modifications. First of all, the rotary potentiometer shown can have more or less than ten dilerent positions.

Considering lthe fact, that there are four different fixed resistors, the maximum amount of possible combinations to attain distinct values of resistances therewith is sixteen, including absence of yall resistors and presence of all of hem. In general, with N different resistors, one can attain 2N different values. rl`his leads to a modification best to be described as a binary set of resistors. Instead of using ohmic values as described, one then will use the values l, 2, 4 and 8 or 10, 20, 40 and 80 etc. The binary system operates so that the unit l is alternately in and out of circuit, unit 2 is alternately twice in then twice out-twice in, etc., unit 40 is four times in, four times tout etc. etc. One .will readily derive from FIG. 1 how ythe shape of the segments will have to be changed to accomplish this; the segment portions alternately contacting any of the o-uter brushes such as 43, 47 or 33, 37 etc., will double in width from one pair of segments to the next looking from right t-o left.

In FIG. 4 is illustrated lanother embodiment of the present invention. There is shown the box for a potentially indefinitely long resistance box or potentiometer. Illustrated are four units, each un-it comprising two double throw switches yand a resistor. Turning specifically to the first one of these units, there are shown two switches 801 and 802. Switch 301 has two resistance contacts, R1 and R2, which are interconnected, and two switching contacts, S1 and S2, which `are also interconnected. Switch 802 has two resistance contacts R3and R4 and two switching contacts S3 and S4;Yhere again resistance contacts and swit-ching contacts are interconnected, respectively. There are also provided power input terminals P1, P2, for switchv 801 and power input terminals P3 and P4 for switch S02. There is a contact maker y803 which may obtain an upper and alower position. In the upper position, the follow .ing respective contacts are made P1 R1, P2 S1, P3 R3, and P4 S3; in the lowerposition, the contacts P1 S2, P2 R2, P3 S4, and P4 R4 are made.

The resistor is denoted with reference numeral 800, in

this vexample yalso indicating its ohmic value. Resistor 864) is connected between contacts R1 and P3. A main power terminal 103 is connected to terminal P1 and the other main terminal 104 which also can be denoted as an output terminal isV connected to terminal P2. Furthermore, terminal S1 is connected directly to terminal P4. This is the circuit connection for the unit which has a circuit connection next to the input terminals 10'3 and 104. The terminals R3 and S3 are connected to the two power input terminals Vof the next switch which in this case is switch 401. The two switches 401 and 402, together with resistance unit 400 are interconnected in a manner similar as are switches 801, 802 and resistor 800. Switches 201 and 202, together with resistor 200 are connected to switches 401 'and 402 and resistor 400 in a manner similar to the manner as the connection of the later elements is connected to the first mentioned unitk (866, Stili and 392). It will be observed that the connections can be made and continued in a similar manner in a practically indefinite succession. In the above instance case there are shown four units, the last one having terminal connecting lines 106 `and 167 which may either be directly interconnected and then connected to a third main terminal 105 (see dashed lines), or the lines lit and its? may be connected to another unit similar to the one shown directly in the drawing.

It will be observed that any resistor is inserted, i.e. is connected between the terminals M53 and 105, when an associated switch and particularly the movable element thereof (such as S63) is in its upper position, while such resistance is connected between terminals 104 and 105, when the associated switch is in its downward position.

This type of circuit connections are made simply by throwing a switch in its upper or in its lower position, and thereby the relative position of the associated resistor is determined regardless of the particular settings of the preceding or of the following unit. In other words, if

kthere is a resistance box of predetermined length, and

therein a resistor has its associated switches in the upper position, this resistor is in circuit while all resistors havhaving the switches in upward position indicates a total ohmic value of the resistances which are in circuit.

If the device as shown in FIG. 4 shall be used `as potentiometer of indefinite length, preferably a unit as illustrated in FIG. 4A is connected to the lines 106 and 167, particularly with the aid of lines 111 and 112, respectively. These lines 111 and 112 lead to two power input terminals of switch M9, having its upper two contacts interconnected by resistance-potentiometer mit (denoting that its total resistance is l() ohms). A main terminal 108 is connected to potentiometer glider 110. In the drawing is shown that the switch 169 has only half the number of contacts as the other units in FIG. 4. 'Ihis is for the simple reason that if a potentiometer is used, there is no need to provide for a particular off-position, because the setting of the potentiometer glider to zero achieves the same result. On the other hand, of course, one can use the twin-type contacts as used in, the units of FIG. 4, and then the potentiometer has also an off position, independent from the setting of its glider. In this case, the handle of the switch also indicates the present position of the potentiometer, and one can thus more readily determine whether the potentiometer is in t fact used or not. FIG. 5 illustrates how a switching arrangementy as illustrated in FIG.' 4 can suitably be used as a variable inductance. The double throw switches lill, 102, 201, 262, 4M, 462, 561 land 502 correspond precisely to the double throw switches w1 to 8d2 of FiG. 4, including their mode of interconnection as well as the four terminals M3, 104, 106 and 107.

However, there are connected to and associated to the Various switches windings m, Til, m, and ll, having one hundred, two hundred, four hundred and five hundred turns, respectively. These windings are provi-ded in lieu of the resistances, 100, 200, 40h and Sti() of FIG. 4,

respectively. These coils or windings are all mounted on a common magnetizable ring core 120, preferably made of iron or other inductance core material. There is provided another coil il? being connected to a primary winding 122 of a transformer 121 the secondary winding 123 of which being connected to the terminals 106 and 167. The secondary winding is further provided with ya glider 124 connected to an output terminal i125. v If winding M has a hundred turns, if the ratio of primary to secondary of transformer 1.21 is large, and if secondary 123 has more than one hundred turns, ya very fine adjustment lrange is obtainable for this inductance as a whole.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departure from the spirit and scope of the invention are intended to be covered by the following claims.

l claim:

l. In a resistance device, a resistor; rst and second, third, and fourth stationary contact means; first, second, and third main terminals; means for completinga series circuit connection between said first and said second main terminal including said first stationary contact means, said first movable contact means, said resistor, said fourth movable contact means and said fourth stationary contact means; means for simultaneously completing a series circuit connection between said second and third main` terminals including said second `and third stationary contact means, and said second and third movable contact means; means for completing a series circuit connection between said first and second main terminal, including said fourth and second stationary contact means and said fourth and secondary rnovabie contact means; means for simultaneously interconnecting said second and said third main terminal via said first kand third stationary contact means, said first and third movable 'contact means, and said resistor; and means for alternating` said series circuit connections.

2. In a resistance device as set forth in claim l, including a potentiometer having a glider associated with said second terminal, said potentiometer being in series circuit connection with said resistor.

3. Resistance device comprising, in combination first, second, third, fourth, fifth, sixth, seventh, eighth, ninth and tenth contact brush means; a first terminal connected to said first and second brush, a second terminal connected to said third brush, means for interconnecting said fourth, sixth and seventh brush, a resistor interconnecting said fifth and said eighth brush, circuit means including a second resistor and a third terminal interconnecting said ninth and said tenth brush., a first contact segment, selectively interconnecting said third and fourth, and said fourth and second brush; a third contact segment selectively interconnecting said sixth and ninth brush and said ninth and said eighth brush, and a fourth contact segment selectively and alternately interconnecting said eighth and said tenth, said tenth and said seventh contact brush.

4. DeviceV as set forth in claim 3,'said second resistor being a potentiometer, the glider of which being associated with said third terminal.

5. In a resistance device; a resistor; a first, second and third terminal; first, second, third, and fourth contact segment; first, second, third and fourth brush means; means for selectively connecting in series Vcircuit connection, said first terminal, said first brush means contacting said third segment, said second terminal, said fourth brush means contacting said fourth segment, said second brush means contacting said second segment, and said third terminal; and means for alternatively selectively connecting in series circuit network connection said first terminal, said first brush means contacting said second segment, said fourth brush means contacting said third segment, said second terminal, said third brush means contacting said fourth segment, said resistor, said second brush means contacting said first segment and said third terminal.

6. in a resistance device as set forth in claim 5 including a potentiometer, said second terminal pertaining to the Vglider of said potentiometer, the latter being interposed between said third and said fourth brush means.

7. In a resistance device; a resistor, a first, second and third main terminal, a first, second, third and fourth contact terminal, means for selectively completing any of the following two circuits: Vfirst main terminal, first power terminal, first contact terminal, resistor, third power ter- 9 minal, third contact terminal, second main terminal, fourth contact terminal, fourth power terminal, second contact terminal, second power terminal, third main terminal; and: first main terminal, first power terminal, second contactterminal, fourth power terminal, third contact terminal, second main terminal, fourth contact terminal, third power terminal, resistor, first contact terminal, second power terminal, third main terminal;

8. In a resistance device as set forth in claim 7 including a potentiometer having a glider said second main terminal pertaining to said glider, said potentiometer being interposed between said third and said fourth contact terminals.

9. Resistance device comprising, in combination terminal means; two contact segments insulated from each other, having similar configuration, insulation'means cooperating with said segments, a first and a second con tact brush electrically connected to one of said segments while said second contact brush is insulated, said second f contact brush making contact with said other one of said segments while said first contact brush is insulated; a third contact brush making contact with said first segment when said second brush makes contact with said second segment, and making contact with said second segment when said first contact brush makes contact with said first contact segment; a fourth and a fifth contact brush making contact with said first and said second segment, respectively; circuit means for connecting said fifth brush to another one of said terminal means and a resistor connected between said fourth brush and said last mentioned terminal means,.said segments being movabley relative to said brushes.

10. Device as set forth in` claim 9,r said resistor being a potentiometer, connected with its other yterminal to vsaid fifthv contact and having a glider terminal, serving asa third terminal means.

11,. In an impedance device of indefinite length; a plurality of resistances, at least one of them havinga different ohmic value than the others; a plurality of pairs of double throw switches each pair having a flrst and a second switch; connecting Vmeans for connecting the movable contacts of the rst switch of onepair of switches to a stationary contact pair of the second switch of the preceding pair of switches; and further connecting means including one resistor of said plurality of resistances for connecting a stationary contact pair of the first switch of each pair of switches to the movable contacts of the second switch of the same pair of switches.

12. In an impedance device as set forth in claim 11, comprising: 4a potentiometer having its stationary terminals connected across a pairV of stationary contacts pertaining to the second switchof the last one of 'said pairs of switches.

13. In an impedance device, an impedance element, first, second and third main terminals, a first, second, third and fourth contact terminal, means for selectively completing any of the following two circuits: first main terminal, rst power terminal, rst contact terminal, impedance element, third power terminal, third contact terminal, second main terminal, fourth contact terminal, fourth power terminal, second contact terminal, second power terminal, third main terminal; and: first main terminal, first power terminal, second contact terminal, fourth power terminal, third contact terminal, second main terminal, fourth contact terminal, third power ter-l minal, impedance element, first contact terminal, second power terminal, third main terminal.

14. In an impedance device: an impedance element; first, second, third, and fourth stationary contact means; first, second, third and fourth movable contact means; first, second, and third main terminals; means for com-` pleting a series circuit connection between said first and said second main terminal including said first stationary contact means, said first movable contact means; said impedance element, said third movable contact means and said third stationary contact means; means `for simultaneously completing a series circuit connection between said second and third main terminals including said second and fourth stationary contact means, and sai-d second and fourth movable contact means; means for completing a series circuit connection between said first and second main terminal, including said third and second stationary contact means said fourth and first movable contact means; means forsimultaneously interconnecting said second and third main terminal via said first and fourth stationary contact means, said second and third movable contact means, and said impedance element; and means for alternating said series circuit connections.

15. In a resistance device; an inductance, a first, second and third main terminal, a first, second, third and fourth contact terminal, means for selectively completing any of thefollowing two circuits: first main terminal, first power terminal, first contact terminal, inductance, third power terminal, third contact terminal, second main terminal, fourth contact terminal, fourth power terminal, second contact terminaL'second power terminal, third main terminal; and: first main terminal, first power terminal, second contact terminal, fourth power terminal, third con`- tact terminal, second main terminal, fourth Contact terminal, third power terminal, inductance, first contact terminal, second power terminal, third main terminal.

16. In an impedance device as set forth in claim 15,

comprising, another winding, a transformer having aprimary connected in parallel to said last mentioned winding and having asecondary connected to a pair of station ary contact terminals of the second switch pertaining to the last one of Ysaid plurality of pairs; and a tap for said secondary forming a main terminal, the movable contact pairs of the first switch of the first pair .of said plurality of switches forming two other main terminals.

@17. In an impedance device of indefinite length: a ring core, a plurality of windings on said core, at least one of them having a different number of turns than the 'rest of the windings on said core; a plurality Vof pairs of double throw switches; each pair having a first and a second switch; connecting means for connecting the movable contacts on the first switch of a pair of switches to a stationary contact pair` of the second switch of the preceding pair of switches; and connector means including one winding for connecting a stationary contact pair of the first switch of each pair of switches to the movable contacts of the second switch of the same pair of switches.

1'8. In an impedance device, an inductance: first, sec` ond, third, and fourth stationary contact means; first, sec ond, third and fourth movable contact means; first, sec-r ond, and third main terminals; means for completing a series circuit connection between said first and said second main terminal including said first stationary contact means, said first movable contact means said inductance, said third movable contact means and said third stationary contact means; means for simultaneously completing a series circuit connection between said second and third main terminals including said second and fourth stationary contact means, and said second and fourth movable conrtacts means; means for completing a series circuit connection between said first and second main terminal, including said third and second stationary contact means and said fourth and first movable contact means; means for sirnultaneously interconnecting said second and third main terminal via said first and fourth stationary contact means, said second and third movable contact means, and said inductance; and means for alternating said series circuit connections.

References Cited in the file of this patent.

UNITED STATES PATENTS i 1,537,927 Blume May 12, 1925 1,801,455 Powell Apr. 21, 1931 v 2,301,884 Kelly Nov. 10, 1942 2,909,750 Pitzer Oct. 20, 1959 

